The present invention relates generally to communication networks and more specifically to the use of location determination and tomography methods and structures in wireless communication networks.
Peer-to-peer network location resolution is an emerging market within the wireless communication arena. New systems are being developed to find people and/or objects, in indoor and outdoor environments. For outdoor environments, there are many solutions that can provide very high-resolution location estimates. In building location solutions, however, techniques are still being researched and developed. Many indoor location determination solutions operate on radio frequency signals and require a dense installation of receivers that can make signal-strength measurements that are used to determine the transmitter""s location. Recently, Bluetooth has been considered a viable solution in the quest to define an indoor solution.
Wireless location determination in Personal Area Networks (PANs) is a function receiving increasing attention. A typical application may be physical security: An office has a collection of computers, printers, lab equipment, etc. and the office manager would like to know the location of this office equipment at all times. To date, this has been done with dedicated hardware. However, it is undesirable to purchase specialized security equipmentxe2x80x94especially if the security function can be performed by equipment already in the office. It would be desirable to use existing wireless data services to perform this additional function without incurring a reduction of data throughput of the system. Device location determination and resolution in this context is not just limited to device connection status, but also to the physical location of the device within the network.
One application of wireless network technology that shows promise in addressing many of the shortcomings of current wireless PANs in terms of cost, throughput, and scalability is Bluetooth. Bluetooth 1.0B is a specification that describes how small, low-cost, low-power devices communicate with each other to facilitate the exchange of information between two devices without the use of a wired connection. Bluetooth devices exist in a PAN in which each subnetwork, called a piconet, contains a maximum of 8 devices. In each piconet, one device acts as a master and the others serve as slave devices. The devices use frequency-hopped spread-spectrum techniques in order to exchange information. In particular, in the United States, at 2.4 GHz frequency, 79 channels are used in a format determined by the master. Each device pseudo-randomly hops among the 79 channels in order to enable multiple-access communications. The Bluetooth Special Interest Group (SIG) decided to break the standard into two documents. The first is called the Core. It specifies components like the radio, baseband modulation, the link manager, the service discovery protocol, etc. The second document is called the Profiles part. It defines the protocols and procedures that must be adhered to for a variety of Bluetooth applications.
One of the shortcomings of the current wireless PAN solutions is their inability to provide low cost, transparent location determination for devices within the PAN. Ideally, each device within the network should have the ability to determine its connectivity status and physical location within the PAN without the use of specialized and expensive hardware and software. A further benefit of an ideal location determination solution would be to combine location and geometry information from several devices within the PAN to make some estimate of the absorption and reflection environment surrounding the PAN. Ideally, location determination calculations could be performed without a corresponding reduction in data throughput between devices within the PAN.